According to the official website, an OVA of Itsuka Tenma no Kuro Usagi was announced to be bundled with the new volume of the novel. The original author Kagami Takaya will write a new episode based on fans' tweets. You can make a request about the episode via twitter with #itsutenanitsuku hash tag.

Oh god....this can only turn out one way....fanservice episode NOOOOOOOOOOOOOOOOOOOOOOOOOO. Well beyond that good luck to them hopefully they will get some decent ideas that will please the fans besides the obvious fanservice morons.